1. Field of the Invention
The present invention relates to an inspection apparatus, and more particularly, to an inspection apparatus suitable for inspecting long pipelines.
2. Background Art
For more than 30 years, video inspection has been a baseline fundamental analytical tool for the evaluation and assessment of pipeline integrity. Originally developed as an aid for sewer system maintenance, video inspection equipment and techniques have played a key role in the development of “no-dig” and “trenchless” pipeline rehabilitation methods. This is because the choice of the best trenchless rehabilitation method, for any given application, is often largely based on the video inspection that takes place prior to the rehabilitation. Thus, the information gleaned from the pre-rehabilitation video inspection is used as the basis for key decisions that drive the entire rehabilitation process.
The inspection of pipes often falls into two broad categories: inspections performed for purposes of preventative maintenance, and inspections performed as a response to a need for repair maintenance. The former category may include such things as locating cracks in the pipeline prior to their reaching a critical length, discovering the location of unknown branches or service tees, determining the exact location of valves and fittings, and finding water within the pipeline. In general, video inspection equipment is useful as a proactive tool for assessing the cleanliness, corrosion, and structural integrity of the pipeline. In the case of repair maintenance, high quality video inspection data is also very important.
Over the years, a myriad of inspection devices have been developed for use inside pipelines. Many of these require a device to carry a camera down the length of the pipeline to capture images that are distant from a manhole, or other pipeline entrance. Other devices rely on a camera having zoom capabilities to capture images at some distance from the pipeline entrance. One such device is described in U.S. Pat. No. 6,538,732, issued to Drost et al. on Mar. 25, 2003. The inspection system described in Drost et al. includes a camera having magnification functionality, one or more lights used to illuminate an object to be imaged, and a power supply and controller for controlling operation of the camera. In addition, the inspection system described in Drost et al. may include a measuring system that can be used to determine the size of an object being imaged.
One limitation of the inspection system described in Drost et al. is that it lacks a mechanism for determining how far the imaged object is from the camera. Thus, an operator will not know where in the pipeline the imaged object can be found. Because a camera may be imaging a portion of the pipeline that needs cleaning or repair, information regarding the specific location of imaged objects is important, and may save both time and money. Another limitation of the inspection system described in Drost et al. is that it needs to be held by an operator to position the camera to capture images of the pipeline. Indeed, even after the camera begins collecting images, the operator is still required to support the device while it is in use. Such a system may lead to operator fatigue, or may result in a reduction in image quality if the operator is unable to hold the camera still while it is capturing images.
Another inspection device is described in U.S. Pat. No. 4,331,975, issued to Krawza et al. on May 25, 1982. Krawza et al. describes instrumentation for surveying underground cavities. The instrumentation includes a television camera and two light sources mounted on a frame which is vertically supported by a cable. The frame assembly is lowered into a bore hole via the cable by a power-driven winch. After being lowered into the bore hole, the frame is supported on the ground by four rubber-capped feet. The instrumentation is configured to provide information about underground cavities, such as mines and caves. For example, cameras attached to the frame can take video or still photographs of the cavity. In addition, the two light sources can be manipulated to provide some information regarding the distance of a cavity wall from the frame. In particular, one of the light sources can be tilted, and if both light sources are focused on the same point, the distance from the frame to that point can be calculated using trigonometry.
One limitation of the instrumentation described in Krawza et al. is that it may not be suitable to inspect pipelines. For example, the video camera is rigidly fixed to the frame, and although the instrumentation may include a pan and tilt mechanism, the camera remains at a fixed distance from the ground. This may not be suitable for inspecting horizontal pipelines, which have a variety of different diameters. Another limitation of the instrumentation described in Krawza et al. is that the position of the frame is not easily manipulated because it is suspended from a cable, rather than having a rigid member attached to it, which would more readily facilitate positioning of the frame. In addition, the system of distance measuring, which relies on two separate lights to focus on the same object, is undesirably complicated, and for horizontal pipeline inspections, it may be unworkable.
Therefore, a need exists for an inspection apparatus capable of providing image and distance information for objects in a pipeline, and capable of being easily positioned, thereby facilitating inspection.